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1080i vs 720p for Xbox 360 and Sony KDSR50XBR1

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8 replies to this topic

#1 of 9 OFFLINE   Chris Bardon

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Posted January 03 2006 - 06:37 AM

So in theory I know what the difference between 1080i and 720p is, but what I'm trying to figure out is what the practical difference is, especially with my new Sony KDSR50XBR1. I know that there's a setting in the 360 dashboard that lets me set 720p or 1080i output (analogue through component cables), but I'm not sure which is the better option. I think it's pretty irrelevant right now, since I don't think there are any games that support 1080i right now, so I suppose it's a question of which setting provides the "best" picture.

Is there some sort of general guideline that people have found as to which setting looks better, or does it really vary from set to set? I've done a search on this section of the forum, and it appears that opinions vary depending on the source and display device.

Anyone else with the same set (or experience with it) care to share some insight?
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#2 of 9 OFFLINE   RAF


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Posted January 03 2006 - 08:24 AM


I addressed this issue in a thread over in the Video Game Software section, but since it is relevant here, I'll reproduce my remarks in this thread rather than just directing you over there.

I said

The simple answer is that 1080i and 720p should look about the same in theory, but in reality, 1080i looks a little bit better for static (still) shots and 720p looks better for action shots (like sports and fast moving video games.) Most people would think they look about the same.

A slightly more detailed answer (but still simplified for the sake of clarity here) is as follows.

720p (or 720 horizontal lines displayed in one frame in the vertical direction) is made up of 1280 horizontal pixels per horizontal line so the resolution (or number of pixels) of 720p = 720 x 1280 = 921,600 pixels per frame.
Note: Some "720p" plasmas display 1280 x 768 lines so their effective resolution is 1280 x 768 or 983,040 pixels.

1080i (or 1080 horizontal lines created from two separate fields of 540 horizontal lines that are interlaced - thus the "i" in 1080i - to produce a single frame are made up of 1920 pixels per horizontal line. So the pixel count of a 1080i frame would be 1920 x 1080 = 2,073,600 pixels per frame. However, since each frame is made up of two fields of 1920 x 540 = 1,063,800 pixel resolution the actual perceived resolution of a 1080i image is really closer to that 1,063,800 pixel figure. And even though 1,063,800 pixels is a higher resolution than the 921,600 pixels of a 720p frame (about 15.4% higher) the interlacing introduces certain artifacts in high motion pictures (like sports and video games) where the fields don't stand still while interlacing takes place. The net effect is that for relatively still shots the 1080i would look better to most people, whereas in fast action shots the 720p would look better because the 921,600 pixels would not be dependent on interlacing additional (moving) information to create the frame. The fact that the 1,063,800 pixels in each field of a 1080i interlaced frame (remember an interlaced frame is made up of two fields) are trying to produce a picture while not really quite in sync for action frames can lead to a less satisfying overall effect.

The bottom line - each has its plusses and minuses and the "1080i for stills and 720p for sports" guideline is a good summary of most people's perception of the situation.

One small footnote: That's why 1080p is such an exciting technology. In 1080p there is no interlacing and the resolution of a 1080p picture is over 2 million pixels (2K technology) - at least twice today's "HD" pictures. When I saw 1080p in action at CEDIA my jaw dropped. And the next step after that is going to be 4K technology.

It never stops. In 25 years people will be reminiscing about the 360 and the PS3 like we do today about Pong (well, not quite, but you get the picture.)

You hit the nail on the head when you said it all depends on the source and the display device. A good rule of thumb (but you can still try out both settings) is to use the setting that represents your display's native setting. The bottom line is that both 720p or 1080i should give you a better visual experience than lesser resolutions - assuming that the source material properly uses the format.
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#3 of 9 OFFLINE   Chris Bardon

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Posted January 03 2006 - 11:49 PM

Robert, thanks for the reply. After I read your quoted post, I remembered that I'd actually read it back in the games forum as well.

Now I just have to figure out how to tweak the VGA input so I can get a decent PC resolution on the TV.
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#4 of 9 OFFLINE   Chris Bardon

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Posted January 10 2006 - 02:50 AM

Just bumping this back up to check out a thought I had just now about this. My TV's manual claims that it displays all inputs in the native 1920x1080 resolution, which should mean that everything is being upconverted to 1080p, no matter what the source, correct? If this is the case, then I really can't decide which would be the better source for upconversion given that I don't know the details of the algorithms.

Either way, this might be veering into "music only dogs can hear" territory Posted Image

As an update, I tried switching the 360 to 1080i the other night, and I noticed a couple of things. The image seemed a little darker, and the text in the 360s menus looked a little different. Not quite sure how to describe it actually. Is it possible that I'd just have to re-adust the brightness/contrast etc after switching to 1080i vs 720p on the 360? I can't see why the input resolution should change anything.

Thanks for all the information!
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#5 of 9 OFFLINE   Jongyoon Lee

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Posted January 10 2006 - 03:59 PM

I don't own Xbox 360, but I heard that the video hardware of Xbox is actually capable of generating 1080 lines of native resolution. In other words, when you select the higher resolution, the hardware will render the video to match the resolution. That's different from simple scaling from 720 lines to 1080 lines on a TV or from a DVD player. If the display is indeed capable of displaying 1080i, you should choose 1080i from Xbox, and you should be able to see a little more detail.

I'm not sure why changing resolution affects the brightness. Maybe the component cable harness doesn't have enough bandwidth for 1080i.

#6 of 9 OFFLINE   Derrik Draven

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Posted January 11 2006 - 07:03 AM

Chris - what tv do you have? I just bought a Samsung HL-R6178 which supposedly does 1080p, as well. It will not accept a 1080 progressive input on it's hdmi or dvi inputs, just the coax and component.

I read somewhere that it does convert the 1080i to a 1080p, internally. Not sure if it's true since, I've read so damn much info on this, I can't remember where I read it!

Anyhoo - I run my 360 on the 1080i output. Everyone tells me too and, doing an a/b comparison with the 720p, I can't hardly tell a difference.

I'd really like to know what sort of artifacts to look for when playing games, to see if, in fact, it's really converting 1080i to 1080p.

All I know is, it has an absolutely stunning picture.
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#7 of 9 OFFLINE   Chris Bardon

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Posted January 11 2006 - 11:33 PM

Like it says in the title, I have a Sony KDSR50XBR1, which is the 50" SXRD (Sony's LCoS offering). Haven't tried going back to 1080i again for any length of time, but I might try again tonight-it appears that I might have to recalibrate for the change though, since the slightly carker picture etc may just be due to the TV remembering settings for different input resolutions? No idea if this is true or not-I just know what I saw.

You're right though, no matter which HD resolution you use, the 360 still puts out a fantastic picture.
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#8 of 9 OFFLINE   David Gotwals

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Posted January 12 2006 - 05:30 AM

I was viewing your TV set at BB last night (It is on the short list for the my new TV). The salesman (who was pretty good for BB standards)said that the upconversion only works for a digital connection, or HDMI, and not the component connectors. I downloaded the manual today (I get obsessive before a purchase), and have skimmed through it, but haven't found this fact. And I believe, please correct me if I am wrong, but it will only convert to 1080i, not 1080p.

If you have some time, give me a short review of the TV.

#9 of 9 OFFLINE   Chris Bardon

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Posted January 12 2006 - 11:46 PM

David, I too checked the manual before buying, and couldn't really find any solid information on this. I also went through a bunch of the 180+ page thread over on AVS, and the consenus seems to be "maybe". While the Sony store rep denied it, it seems that the HDMI ports will convert a 1080i signal to 1080p, and a 1080p signal will only input as 1080i, but will then be converted to 1080p by the TV. No idea on the component connections though.

I actually tried the 1080i setting on the 360 for a little while last night, and I think I'm sticking with 720p. It looked a little smoother playing perfect dark, although I think most of the jerkiness I saw was the game (opening cinematic of mission 4 for those who are curious). For some reason the screen text just seemed a little harder to read in 1080i though, and I have no idea why. I'm by no means an expert on these kinds of things though, and at this point I'm just happy that the TV looks really good, and that I can play 360 games in HD.

As for a review of the set, this TV is way better than any other projection TV I've seen so far. I comapred it to the 50" grand Wega that my dad bought last year, and noticed the better contrast ratio, black levels, and colours right away. I also like the fact that the SDE is nonexistent on this set, but more prevalent on the older models if you're a little closer to the screen. I calibrated the set using the THX optimode on Revenge of the Sith (at least on the DVD input), and my regular 480p DVD player looks really good. The TV says that the signal is 480p, but I have no idea whether there's an internal upconverter or not. Either way, I watched Sin City on it the other night, and the picture was nice and black.

Only caveat so far is that the PC input on this thing is a piece of garbage. The best it can do is 1280x1024, which doesn't come close to filling the screen (no zoom modes or 16x9 resolutions either). IMO, this was a major fumble on Sony's part. Luckily, a DVI->HDMI cable is letting me get 720p from an HTPC, and I've seen reports that 1080p is possible with this setup. Again though, I have no idea how to actually tell the difference, so I can't really comment.

If you have any other specific questions about the set though, let me know.
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